Occupant restraint systems for use in vehicles are well known in the art. One such restraint system includes a crash sensor, an inflatable airbag, and an actuation circuit that controls deployment of the airbag in response to an output from the crash sensor. The crash sensor can be an accelerometer that provides an electrical signal having a value functionally related to the vehicle's deceleration. The actuation circuit includes a squib operatively connected to a source of inert gas.
During a crash condition of a vehicle, the vehicle's accelerometer provides a signal indicative of such crash condition. The actuation circuit thereby applies a current through the squib which causes the squib to ignite. When the squib ignites, the source of inert gas discharges gas into the airbag, which results in inflation of the airbag.
Certain vehicles have both a driver side airbag and a passenger side airbag ("dual airbags"). If such a vehicle is occupied only by the driver and is involved a crash, deployment of the passenger side airbag is unnecessary. Unnecessary deployment of the passenger side airbag can increase the cost of repairing the vehicle. Since a large percentage of vehicles on the highway are occupied by only the driver, it is desirable to (i) be able to detect if a passenger is present in the vehicle and (ii) deploy the passenger side airbag during a crash only if the passenger is, in fact, present.
The prior art has recognized the problem of unnecessary deployment of a passenger side airbag during a crash when no passenger is present. Prior art occupant restraint systems having dual airbags have provided various forms of occupant sensors and have enabled the passenger side airbag only when an occupant is present in the passenger seat.